1. Field of the Invention
This invention relates to a process for the production of alkyl and/or alkenyl oligoglucosides by drying of an aqueous glucose/fatty alcohol suspension and subsequent acetalization of the dried mixture in the presence of acidic catalysts.
2. Statement of Related Art
Alkyl oligoglycosides are important nonionic surfactants for a number of applications. They are generally produced by acetalization of aldoses (mainly glucose) with fatty alcohols in the presence of acidic catalysts (direct process). However, to obtain high yields in sufficiently short reaction times, it is of advantage to carry out the reaction in the absence of water. More specifically, this means that only water-free starting materials, i.e. starting materials with a residual water content of not more than 2% by weight, may be used for the acetalization. International patent application WO 90/3977 is cited as representative of the extensive literature available on this subject.
The use of pure materials, for example pure water-free glucose, adds to the costs involved in the production of alkyl oligoglucosides to such an extent that economic production is often impossible. Accordingly, there has been no shortage of attempts in the past to use technical glucose based on inexpensive water-containing glucose sirups which have been dried to the necessary extent [EP-A1 0 319 616]. However, a major disadvantage in this connection was found to be that conventional drying processes always influence the quality and composition of the water-free products and, in particular, can contribute towards an unwanted increase in the content of oligosugars and polysugars.
Accordingly, the problem addressed by the present invention was to provide a new process for the production of alkyl and/or alkenyl oligoglucosides which would be free from the disadvantages mentioned above.